Mayweather announced that he will return to the ring for the first time in nearly a year to fight Guerrero on May 4 at the MGM Grand in Las Vegas.

Guerrero (31-1-1 with 18 knockouts), nicknamed "The Ghost," must fill a tall order in facing the undefeated Mayweather (43-0, 26 knockouts) for the World Boxing Council welterweight title. Mayweather is regarded as the best pound-for-pound fighter in the sport, not that Guerrero puts too much stock in that,

"I am going to shock the world," Guerrero said. "The fans pushed for this fight, and I will win for them. I don't think Floyd wanted to fight me."

The bout is part of a new six-fight deal between "Money" Mayweather, 35, and Showtime, as the popular fighter has left HBO. Showtime and parent company CBS will heavily promote Mayweather-Guerrero during March Madness and have plans for a lead-in series on the fighters.

"This will be the biggest sporting event of 2013, no question," Luis DeCubas Jr., Guerrero's co-manager, said. "The Bay Area has never had a boxer in a fight of this magnitude. This is the next Super Bowl."

Guerrero, 29, earned the fight with an impressive win over former welterweight world champion Andre Berto in November, in which he knocked down Berto in the first and second rounds. That landed the southpaw with a good chin on Mayweather's radar, Mayweather adviser Leonard Ellerbe said.

"He's a very good fighter and has a great story and deserved the opportunity," Ellerbe said of Guerrero, the WBC interim welterweight champion. "Floyd has fought southpaws before. He'll handle this fight as he's handled them all."

Guerrero "won the Mayweather sweepstakes," Ellerbe said, "so now he gets to see what the grand prize is, and when he opens up that grand prize, it's going to be a can of ass whooping."

Guerrero took more than a year off from the sport to help his wife, Casey, successfully battle leukemia - a story line that Showtime and CBS will be sure to explore.

DeCubas said Guerrero will make more than Victor Ortiz did when he fought Mayweather in 2011. Ortiz made $2 million. Mayweather, a huge pay-per-view draw, made more than $25 million in that fight, and more than $32 million for his win over Miguel Cotto in May.

Mayweather turns 36 Sunday, but the unbeaten WBC 147-pound champion has shown no signs of age in the ring. He spent two months in jail last summer after his conviction in a misdemeanor domestic battery case.

"He has a renewed motivation to stay active and to take on everybody out there," Ellerbe said. "When Floyd is more active, he's going to be beyond untouchable. He's proved he can stay sharp with those layoffs in the past, but he's going to be more active now."

DeCubas said Guerrero almost got Mayweather a pair of socks for his birthday Sunday.